The present disclosure relates to a radiation-source-to-image-surface distance obtainment apparatus, method and program that obtains a radiation-source-to-image-surface distance, which is a distance between a radiation source that outputs radiation to a subject and a detection surface of a detection means that detects radiation that has passed through a subject. Further, the present disclosure relates to a radiographic image processing apparatus, method and program that performs image processing on a radiographic image by using the radiation-source-to-image-surface distance.
Conventionally, in performing radiography on a subject by radiation passed through the subject, there is a problem that radiation is scattered in the subject, and this scattered radiation (hereinafter, referred to as scattered radiation) lowers the contrast of an obtainable radiographic image. Therefore, radiography is performed, in some cases, by arranging a scattered radiation removal grid (hereinafter, simply referred to as a grid) between a subject and a detection means, such as a radiation detector for obtaining a radiographic image by detecting radiation, so that the detection means is not irradiated with the scattered radiation. If radiography is performed by using the grid, the detection means tends not to be irradiated with radiation scattered by the subject. Therefore, it is possible to improve the contrast of the radiographic image.
Meanwhile, if radiography is performed by using a grid, a stripe pattern (grid stripe) corresponding to the grid is included in a radiographic image together with a subject image, and observation of the image becomes difficult. Therefore, scattered radiation removal processing in which radiography is performed without using a grid, and an effect of improving image quality that would be achievable by removal of scattered radiation by a grid is given to the radiographic image by image processing has been proposed (please refer to Japanese Unexamined Patent Publication No. 2014-207958 (Patent Document 1) and Japanese Unexamined Patent Publication No. 2015-043959 (Patent Document 2)). Patent Document 1 proposes a technique for performing scattered radiation removal processing based on virtual grid characteristics, in which a virtual grid is assumed. Further, Patent Document 2 proposes a technique for performing scattered radiation removal processing by estimating the body thickness of a subject.
Further, in recent years, so-called portable radiography, which uses a portable-type radiation irradiation apparatus and a portable-type detection means, has been performed. The weight of a radiation irradiation apparatus for performing portable radiography has been reduced to such a degree that an operator can operate the radiation irradiation apparatus held by his/her hand or hands, and it is easy to carry the radiation irradiation apparatus. Therefore, radiography of a subject is possible at various locations, for example, such as a patient's room in a hospital and a natural disaster site.